Caption: Hydra. Differential interference contrast (DIC) light microscopy footage of a hydra, a microscopic aquatic invertebrate of the phylum Cnidaria. These freshwater predatory animals have typical cnidarian features: radial symmetry, saclike bodies with only one opening, and stinging tentacles for catching prey. They spend their entire lives as sedentary polyps and are hermaphrodites, where each hydra has testes on its stalk that can fertilise any eggs. This clip was filmed with darkfield illumination.